Conventionally, in a device with a shaft that rotates at high speed, e.g., high speed electric motor or a turbocharger, an oil film damper is placed in a rotary bearing to prevent vibration of the shaft.
For example, a conventional turbocharger has a shaft which rotates at a high rotational velocity. The shaft is supported by an angular ball bearing and damper. A lubricating oil is filled in a gap created between the damper and a side brake and the angular ball bearing is stably supported by the damping effect of the oil film.
However, the amount of the supplied lubricating oil is constant regardless of the rotational velocity the shaft. It is possible for vibration of the shaft to occur at particular rotational velocities.